Use preempt_schedule_irq to prevent infinite irq-entry and
eventual stack overflow problems with fast-paced IRQ sources.
This kind of problems has been observed on the PASemi Electra IDE
controller. We have to make sure we are soft-disabled before calling
preempt_schedule_irq and hard disable interrupts after that
to avoid unrecoverable exceptions.
This patch also moves the "clrrdi r9,r1,THREAD_SHIFT" out of
the #ifdef CONFIG_PPC_BOOK3E scope, since r9 is clobbered
and has to be restored in both cases.
Signed-off-by: Valentine Barshak <vbars...@ru.mvista.com>
---
arch/powerpc/kernel/entry_64.S | 25 ++++++-------------------
1 file changed, 6 insertions(+), 19 deletions(-)
diff -pruN linux-2.6.orig/arch/powerpc/kernel/entry_64.S
linux-2.6.new/arch/powerpc/kernel/entry_64.S
--- linux-2.6.orig/arch/powerpc/kernel/entry_64.S 2009-10-17
03:46:26.000000000 +0400
+++ linux-2.6.new/arch/powerpc/kernel/entry_64.S 2009-10-19
17:35:16.000000000 +0400
@@ -660,33 +660,20 @@ do_work:
bne restore
/* here we are preempting the current task */
1:
-#ifdef CONFIG_TRACE_IRQFLAGS
- bl .trace_hardirqs_on
- /* Note: we just clobbered r10 which used to contain the previous
- * MSR before the hard-disabling done by the caller of do_work.
- * We don't have that value anymore, but it doesn't matter as
- * we will hard-enable unconditionally, we can just reload the
- * current MSR into r10
- */
- mfmsr r10
-#endif /* CONFIG_TRACE_IRQFLAGS */
- li r0,1
+ /* ensure we are soft-disabled */
+ li r0,0
stb r0,PACASOFTIRQEN(r13)
- stb r0,PACAHARDIRQEN(r13)
+ bl .preempt_schedule_irq
+ /* hard-disable interrupts */
#ifdef CONFIG_PPC_BOOK3E
- wrteei 1
- bl .preempt_schedule
wrteei 0
#else
- ori r10,r10,MSR_EE
- mtmsrd r10,1 /* reenable interrupts */
- bl .preempt_schedule
mfmsr r10
- clrrdi r9,r1,THREAD_SHIFT
- rldicl r10,r10,48,1 /* disable interrupts again */
+ rldicl r10,r10,48,1
rotldi r10,r10,16
mtmsrd r10,1
#endif /* CONFIG_PPC_BOOK3E */
+ clrrdi r9,r1,THREAD_SHIFT
ld r4,TI_FLAGS(r9)
andi. r0,r4,_TIF_NEED_RESCHED
bne 1b
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